Humans are the only mammals that regularly walk upright on two legs. Walking upright creates many advantages that have enabled our species to succeed. However, walking upright also imposes increased loads on the lower back muscles because they must help support the upper torso. As a consequence, lower back problems due to weak lower back muscles are very common. Lower back problems are especially common among men. For this reason and for brevity, masculine pronouns are used herein.
A variety of exercises are commonly performed to strengthen the lower back muscles. In one common exercise, the user sits on a machine with a movable pad resting against his lower back. The lower back pad is connected to a stack of weights so that its resistance to movement can be varied. The user exercises the lower back by leaning backwards to move the pad against the resistance. This exercise is not advisable for users with spinal column problems because the motion causes compression of the discs in the spinal column.
Another common exercise is known as a back extension or hyperextension. The user faces downward on a bench (commonly known as a Roman chair) that supports his lower body. The bench may be horizontal or may be angled. The user then lowers the upper body by pivoting forward and downward, and then raises his upper body back to the starting position. The weight of the user's upper body (the downward gravitational force) provides the resistance to the upward motion. The back extension does not compact the spinal column and additional resistance is easily added by the user extending his arms or holding a weight.
Unfortunately, many persons with lower back problems have insufficient strength to perform an unassisted back extension. In other words, their lower back muscles are too weak to lower and raise their upper bodies. The only way such persons can perform back extensions is to have another person, such as a physical therapist, trainer, or partner, assist the motion by lifting the upper body. The term “assist” is used herein to refer to anything that reduces the muscular force needed to raise the upper body when performing a back extension. In other words, the term is not used to connote the presence of another person.
Wu, U.S. Pat. No. 6,939,272, Sep. 6, 2005, discloses an exercise machine for performing abdominal and lower back exercises. The machine contains a stationary pad and a pivoting pad. The movement of the pivoting pad is resisted by the stack of weights. A large number of exercises are performed on the machine. FIG. 15 illustrates an exercise for the lower back in which the user lays on his back and moves the pivoting pad downward. FIG. 16 illustrates an exercise for the abdominal muscles in which the user lays on his stomach and moves the pivoting pad downward. Wu does not disclose the use of the machine for back extensions.
Accordingly, there is a demand for an exercise machine that provides variable assistance, rather than resistance, to a user performing a back extension. There is also a demand for a method of performing assisted back extensions without the presence of another person.